Method of producing carbon granules



Oct. 20, 1931- E. EBLANKENSTEIN METHOD OF PRODUCING' CARBON GRANULES Filed Dec. 28, 1927 Patented er. 20.1931- UNITED STATES.

" PATENfn vorrlcl.

EDWARD Evans BLANKNsrEm, or CHICAGO,

p Tmc comm, nrconroaarnn, or NEW Yonex,

YORK

N.-Y., ACORIPORATION OF NEW .METHOD OF-PRODUCING CARBON GRANULES Application mea December as, 1927. serial- No. 243,011.

- variation can be made more nearly proportional to the pressure-variation upon the car- .bon particles. In some instances where irregularly shaped particles havebeen used there is a. tendency for the sharp points of the carbon to penetrate the thin walls of the container of the unit and thu'scause a leakage of the carbon from the container, thereby impairing the eiciency of the unit. 2 'Anbject of he invention is to providean economical method for producing carbon in a very eiiient formlfor use invariable resistance units.. d

.In accordance with the general features of the invention, a yparticle of carbonizable material in liquid or plastic form is isolated from a mass of such material and subjected to conditions which permit the Jparticle to assume a spherical shape due to the surface I tension of the material. 'Ihe spherical pellet thus formed is then hardened and carbonized to form a spherical carbon granule which is in a form particularly' suitable for use in telephone transmitters. l

85 ,It is believed that a complete understandmg of the invention may be had by reference to the following descrlption taken in coillunction with the accompanying drawing Y which'illustrates a method in accordance with the invention. f

A receptacle 4 is shown partially filled with a carbonizable material 5finla liquid form, which may consist of vegetable fibers or cellu/lose dissolved in a `solution of zinc chloride .45 or any other material commonly used as lila? ment stock for carbon filaments such as are employed in incandlgscent lamps. The carbonizable material extruded from the receptacle .in the formof a heavy liquid throu h a nozzle 6 by 'exerting an" air pressureon the interior of the receptacle through a tube 7 leading to a suitable ressure system (not shown). A revolving ife 8 driven by any suitable means (not shown), and having a ,plurality of blades is positioned so that the revolving blades pass through the path of the extruded material and the rate of revolution ILLINOIS, ASSIGNOR T0 WESTERN ELEC- of the blades with respect to therate of ex- 'trusion of the material is such that masses of the material of suitable size will be isolated from one vanother permitting th'e surface tension of the masses to draw them into spherical form. I I

The pellets of carbonizable materlal thus formed are deposited in an alcohol bath 9 in a long container. 10 several feet in height -which gives the pellets suicient time to solidify an harden before reaching the base of the container where they accumulate and come 1n contact with one another. In the -alcoholbath the pellets are reduced considerably in size and become suiicientlyhard to bear handling. pears to aid in the formation of the spheres which may be due to the fact that the cellulose material is not soluble o'r miscible in the alcohol, and also to impart a tenacious outer skin to the pellets. After the elletshave been retained in the alcohol a su cient length of time they are removed and dried. l

. The cellulose pellets are carbonized by heating them in an inert atmosphere such as a hydrogen atmosphre which prevents oxidation of the material. The pellets are first heated toa comparatively low temperature for an extended period to expel any volatile substance contained therein after which the..

temperature is raised suiiiciently high to carvbonize the material leaving it in the form of `spherical `carbon granules.

It has been found that spherical carbon granulesformed as described above are particularly well adapted for use in sound.

transmitting devices having what is known as b5 a ioatingdiaphragm which 'is resiliently supported. The spherical granules have no appreciable tendency to work their way out o their vcontainer through the juncture be?. tween the container and the diaphragm. VWhen the spherical particles areused in va- The alcohol treatment apriable resistance units very satisfactory results are also obtained due to the fact that the spherical anules can conveniently be made of a su stantially uniform size and vtherefore a more uniform variation of the,

resistance will result.

It will be understood that the illustration of the invention herein described is merely a convenient and usefuljorm ofthe inventlon which is capable of many other-modifications Without departing from the spirit and scope of the invention.l

What is claimed is:

1. A method of producing spherical carbon granules, which comprises extruding a stream of cellulose dissolved@ in a water solution of zinc chloride,l brealn'n'g the stream into iso` lated particles to cause the particles to assume arspherical shape, depositing the particles in a bath of`alcohol spherical carbon granules.

2. A method of roducing carbon granules, which comprises orming a solution of cellulose `in a water solution lof zinc chloride into small particles, passing the articles throu h alcohol to harden them, and particles.

In witness whereof; I hereunto subscribe llrname this 16th day of December, A. D.

` EDWARD EVANS BLANKENSTEIN.

to solidify them, and car- ,l bonizing` the spherical particles to form` carbonizing t e I 

